The present invention relates to cured tobacco. More particularly, the present invention relates to a novel bright tobacco filler and to tobacco blends and smoking articles containing this tobacco.
Of the more than sixty genetic species of plants belonging to the genus Nicotiana, only two of them, N.tabacum and N.rustica, are cultivated for use as tobacco. The first is grown in appreciable amounts in nearly 100 countries throughout the world and constitutes the tobacco of commerce, whereas the second is grown extensively in parts of Eastern Europe and Asia Minor.
N.tabacum is a natural hybrid between N.sylvestris and N.otophoria and is a plastic, very adaptable. polymorphic species as evidenced by the different types and the numerous agronomic varieties in each of the types. The commercially important types are known as Virginia or flue-cured, burley, Maryland, cigar tobaccos, and oriental or aromatic, tobaccos, all of which are used in the manufacture of smoking articles such as cigarettes, cigars and cigarillos.
Tobacco is cultivated widely throughout the world, indicating that it is adaped to a wide range of edaphic (i.e., soil) and meterologic (i.e., climatic) conditions. The leaf produced in each locality differs from leaves produced in the other localities. Both edaphic and climatic factors vary in each tobacco-growing locality, but they also vary appreciably in any given locality from year to year. Each factor is capable of modifying the physical and chemical properties of the leaf produced.
A cured tobacco leaf is not just a dried leaf of tobacco. Each green leaf on any given plant differs from all of the other leaves in age, size, color, proportion of length to width, thickness, and amounts and distribution of chemical constituents. Consequently, the cured leaves differ markedly in physical and chemical features and these differences constitute, in part, the basis for commercial grades of leaf. These physical and chemical differences correlate with the position at which the leaf is borne on the stalk, and the stalk position serves as the primary basic for classification of leaf in the grades.
Certain cultural practices are employed to cause physical and chemical changes in the leaf. These practices include topping, suckering, priming, and the application of mineral and organic fertilizer as well as of suckering inhibitors. "Topping" is the term applied to the removal of the inflorescence. "Suckering" applies to the removal of axillary buds that grow after the plants have been topped. "Priming" means removal of leaves at successive intervals, as they mature. The number of primings, usually 5 to 8 depends upon the type of tobacco and the kind of weather that prevails throughout the harvesting. Essentially all flue-cured tobaccos are harvested by the priming method. Nearly all burley tobaccos are stalk-cut in the United States but may be either primed or stalk cut in other tobacco-growing countries.
Once the mature green leaf is harvested, it is subjected to such conditions of humidity and temperature as will permit it to cure. There are essentially four kinds of curing processes, namely, flue-curing, air-curing, fire-curing and sun-curing, each of which is an aerobic process. Virginia tobacco is flue-cured while burley is air-cured. A distinctive difference between air-curing and flue-curing is that in the air-curing process the soluble sugars content of burley is reduced essentilly to zero due to oxidations that were mostly inhibited during the flue-curing process but which occur during the air-curing process.
Curing is characterized by two processes, one of which is dehydration or water loss, and the other of which is a series of chemical changes. At the end of curing, the water content has been reduced by 80to 90% of the green leaf weight and various color changes have occurred which are due primarily to the destruction of chlorophyll and various browning reactions. The most pronounced of the chemical changes is the conversion of starch into soluble disaccharides and monosaccharides. Oxidative decompositions involving the proteins also occur but are relatively small compared to the changes in carbohydrates. Nicotine losses during curing are on the order of about 0.10%. Losses of volatile substances, about 7%, take place in the waxy, resinous materials, and the demethylation of pectins is appreciable. During the early stages of curing, respiration and other life processes occur, but they cease when the loss of water reaches a certain point. Thereafter, numerous enzymes continue to act but at reduced rates, although with flue-curing, in which the reaction rates are faster than in air-curing, many enzymes, especially the proteases, are destroyed by the heat applied during curing and thus do not continue to act.
The bulk of the tobacco is subjected to a redrying and then an aging process before it is incorporated into smoking articles. During redrying, the leaves are reheated in redrying machines in which the temperatures are raised at intervals of 80.degree. C. or until the moisture content has been reduced to about 6% and then the leaves are permitted to reabsorb moisture under controlled conditions until their moisture content is about 9 or 10%. The leaves are then packed into hogsheads having a capacity of about 1,000 pounds or into similar such containers and then are stored 1 to 3 years to undergo aging. Instead of packing bundles of redried leaves, blade tissue may be separated from midribs by means of special threshing machines prior fto redrying, and the midribs and blade tissues packed separated. There is very little change in the chemical composition of the leaves during redrying.
American brands of cigarettes contain different proportions of different grades of Virginia, burley, Maryland, and oriental tobaccos as well as shredded or expanded stems and reconstituted tobacco. Casing solutions are added to burley blended tobaccos. Humectants, consisting of glycerol and glycols, are also added before cutting. The blend is passed through cutting, drying, and then cooling machines in which alcohol-soluble flavors such as fruit extractives, tonka bean extract, menthol, oil of peppermint, oil of cloves, oil of cinammon, or other aromatic substances may be applied. After storage for several hours, the tobacco is fed to the cigarette-making machines.
As used herein, the following terms have the indicated meanings.